The long-term objectives of this program are to study the structure of nucleosomes and other key macromolecular constituents of genetic material. These macromolecules are elements in the primary functions of chromatin: transcription and regulation, replication and DNA packaging. In order to understand the function of these molecules, several biophysical and biochemical techniques will be emphasized, with the primary effort consisting of (1) x-ray crystallography of nucleosomes and (2) studies of the macromolecular components of genetic material in solution using the technique of small-angle neutron scattering (SANS) and small angle x-raly scattering (SAXS). The x-ray crystallography program will consist of the study and interpretation of a low resolution 6-8 Angstroms electron density map of the nucleosome, development of nucleosome crystals which diffract to medium or high resolution (about 3 Angstroms) to be accomplished by reconstituting nucleosomes from the purified histones and a DNA component of defined length and sequnce, and determination of the structure by crystallographic methods. The small-angle scattering program will concentrate on materials closely associated with potentially active genes, such as HMG - nucleosomes, "active nucleosomes", and other chromatin species such as dinucleosomes.